package servlet;

import pojo.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

@WebServlet(urlPatterns = {"/user"})
public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<User>users = new ArrayList<>();
        //jdbc操作数据库 查询

            //1.加载驱动
            try {
                Class.forName("com.mysql.cj.jdbc.Driver");

                //2.获取连接
                String url="jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=utf-8";
                try {
                    Connection connection = DriverManager.getConnection(url, "root", "123456");
//                if (connection!=null){
//                    System.out.println("连接成功");
//                }

                    //3.写sql
                    String sql="select * from user";

                    //4.预编译sql
                    PreparedStatement preparedStatement = connection.prepareStatement(sql);

                    //5.有参数设置参数

                    //6.执行sql
                    ResultSet resultSet = preparedStatement.executeQuery();

                    //7.遍历结果集
                    while (resultSet.next()){
                        User user = new User();
                        user.setId(resultSet.getInt(1));
                        user.setName(resultSet.getString(2));
                        user.setPass(resultSet.getString(3));
                        //把对象添加到集合中
                        users.add(user);

                    }

                    //8.关闭资源
                    resultSet.close();
                    preparedStatement.close();
                    connection.close();

                    //把集合中数据存储到作用域中
                    req.setAttribute("users",users);
                    //打开页面
                    req.getRequestDispatcher("/user.jsp").forward(req,resp);

                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }

            } catch (ClassNotFoundException e) {
                throw new RuntimeException(e);
            }

        }
    }

